Friday, December 14, 2012

Burning brush piles

The first snow of the winter is a great time for burning brush piles and yesterday was the day.

Each year we create a "generic" brush pile on the edge of the Valley Prairie adjacent to Pleasant Valley Road where slash, and woody stuff and bags of weeds are tossed We start in early summer and continue through the rest of the year. By early December this pile is dry and burns well.

Most of the piles we burned yesterday were in the lower part of the North Woods, just uphill from County F. These piles had been created via restoration work done on a LIP grant last winter. Since they were really dry they burned very well.

There is an "art" to building a good brush pile. All of the 13 piles we burned yesterday had been built by Amanda last winter. As the photo above shows, these piles are fairly compact but the sticks are not so tight that air can't get in. In order to build piles like these, you need to cut off side branches, since they keep the sticks from lying horizontal and in parallel. Also, once the pile gets fairly large, it helps to jump on it from time to time and push it down.

The crew got all 13 piles burning well and then went off to lunch. By the time they returned, each pile was mostly burned down, but there are always outlier sticks and branches that escape the fire. Time for consolidating.

Consolidating a brush pile is an art in itself. The ideal tool is a pitchfork, which works well to pick up partially burned branches and twigs. All unburned material is thrown into the burning center of the pile, where it quickly catches fire. Bigger logs can be picked up by hand and tossed onto the fire. Heavy duty leather gloves are essential here, since they are fire- and scuff-resistant.

By the time you return the next day, there should be lots of ash but very little unburned material. If the area under the burn pile is to be planted, the ashes should be blown away with a powerful leaf blower so that the seeds can reach the mineral soil. Because of the intense heat, the underlying soil is essentially sterile. Although it will eventually get colonized on its own, it is best to short-cut this lengthy succession process by using plant species that are adapted to the particular habitat.

Sunday, December 9, 2012

Controlling prairie willow at Black Earth Retttenmund Prairie

Yesterday our monthly work party at Black Earth Rettenmund focused on controlling the large amount of prairie willow (Salix humilis) that threatens to take over the top of the knoll on the North Unit.

About 8 years ago, when we did major brush work on the North Unit, we left the native prairie willow when removing all the nonnative shrubs. We assumed that because it was native, and had the word "prairie" in its common name, that it should be allowed to remain. At that time there were only a few small clumps. About three years ago we suddenly realized that the willow had spread greatly, and was now starting to shade out prairie forbs and grasses. The biennial burns that should have held it back were not doing their job. Since the North Unit had lots of important prairie species, we decided we needed to control the willow.

Prairie willow grows in clumps with a variable number of stems. (My counts yesterday ranged from 11 to 84 stems.) No rhizomes are formed, so an individual plant is rarely more than a couple of feet wide and about knee-high. I haven't followed individual plants but according to the horticultural literature it is moderately short lived. It flowers early in the spring (the buds are like pussy willows), and spreads by seeds. At Black Earth Rettenmund we have seen it spread widely on the North Unit, but it has not appeared elsewhere at the site.

In May of this year we had a volunteer work party which controlled brush on the North Unit. At that time, prairie willow was the primary target. See this link for details, including growing-season photos. Soon we became occupied with sweet clover control followed by seed collecting and it was only now that we could return to willow. Since we plan to burn the North Unit in the spring, it was important to deal with the willow now.

Yesterday a small but dedicated group of volunteers helped us attack the willow. Some people used hand clippers or loppers, treating the cut stems with Garlon 4 in oil. Because the willow stems are quite thin, the cut stems present very little surface for herbicide, so that the herbicide was used as a basal bark.

Mark working at the top of the North Unit. In the foreground is a large willow plant with over 50 living stems. These clumps can be easily spotted this time of year by the distinct red color of the stems.

In fact, you don't really need to cut the stems, and at this time of
year, when there is no foliage, each stem of a clump can be easily
herbicided with the paint sponge technique. The photo below shows this working on a small clump.

Close up of the center of a willow clump. At this time of year, when there is no foliage, it is easy to basal bark stems with the paint sponge stick.